Add basic file mapping support.

pdal/util/FileUtils.cpp

@@ -32,13 +32,16 @@
 * OF SUCH DAMAGE.
 ****************************************************************************/
 
+#include <fcntl.h>
 #include <sys/stat.h>
 
 #include <iostream>
 #include <sstream>
 #ifndef _WIN32
 #include <glob.h>
+#include <sys/mman.h>
 #else
+#include <io.h>
 #include <codecvt>
 #include <Windows.h>
 #endif
@@ -444,7 +447,79 @@ std::vector<std::string> glob(std::string path)
     return filenames;
 }
 
-} // namespace FileUtils
 
+MapContext mapFile(const std::string& filename, bool readOnly,
+    size_t pos, size_t size)
+{
+    MapContext ctx;
+
+    if (!readOnly)
+    {
+        ctx.m_error = "readOnly must be true.";
+        return ctx;
+    }
+
+#ifndef WIN32
+    ctx.m_fd = ::open(filename.c_str(), readOnly ? O_RDONLY : O_RDWR);
+#else
+    ctx.m_fd = ::_open(filename.c_str(), readOnly ? O_RDONLY : O_RDWR);
+#endif
+
+    if (ctx.m_fd == -1)
+    {
+        ctx.m_error = "Mapped file couldn't be opened.";
+        return ctx;
+    }
+    ctx.m_size = size;
+
+#ifndef _WIN32
+    ctx.m_addr = ::mmap(0, size, PROT_READ, MAP_SHARED, ctx.m_fd, (off_t)pos);
+    if (ctx.m_addr == MAP_FAILED)
+    {
+        ctx.m_addr = nullptr;
+        ctx.m_error = "Couldn't map file";
+    }
+#else
+    ctx.m_handle = CreateFileMapping((HANDLE)_get_osfhandle(ctx.m_fd),
+        NULL, PAGE_READONLY, 0, 0, NULL);
+    uint32_t low = pos & 0xFFFFFFFF;
+    uint32_t high = (pos >> 8);
+    ctx.m_addr = MapViewOfFile(ctx.m_handle, FILE_MAP_READ, high, low,
+        ctx.m_size);
+    if (ctx.m_addr == nullptr)
+        ctx.m_error = "Couldn't map file";
+#endif
+
+    return ctx;
+}
+
+MapContext unmapFile(MapContext ctx)
+{
+#ifndef _WIN32
+    if (::munmap(ctx.m_addr, ctx.m_size) == -1)
+        ctx.m_error = "Couldn't unmap file.";
+    else
+    {
+        ctx.m_addr = nullptr;
+        ctx.m_size = 0;
+        ctx.m_error = "";
+    }
+    ::close(ctx.m_fd);
+#else
+    if (UnmapViewOfFile(ctx.m_addr) == 0)
+        ctx.m_error = "Couldn't unmap file.";
+    else
+    {
+        ctx.m_addr = nullptr;
+        ctx.m_size = 0;
+        ctx.m_error = "";
+    }
+    CloseHandle(ctx.m_handle);
+    ::_close(ctx.m_fd);
+#endif
+    return ctx;
+}
+
+} // namespace FileUtils
 } // namespace pdal
 

pdal/util/FileUtils.hpp

@@ -43,6 +43,10 @@
 #include <string>
 #include <vector>
 
+#ifdef _WIN32
+#include <Windows.h>
+#endif
+
 #include "pdal_util_export.hpp"
 
 namespace pdal
@@ -258,6 +262,45 @@ namespace FileUtils
       \return  List of files that correspond to provided file specification.
     */
     PDAL_DLL std::vector<std::string> glob(std::string filespec);
-}
 
+
+    struct PDAL_DLL MapContext
+    {
+    public:
+        MapContext() : m_fd(-1), m_addr(nullptr)
+        {}
+
+        void *addr() const
+        { return m_addr; }
+        std::string what() const
+        { return m_error; }
+
+        int m_fd;
+        size_t m_size;
+        void *m_addr;
+        std::string m_error;
+#ifdef _WIN32
+        HANDLE m_handle;
+#endif
+    };
+    /**
+      Map a file to memory.
+      \param filename  Filename to map.
+      \param readOnly  Must be true at this time.
+      \param pos       Starting position of file to map.
+      \param size      Number of bytes in file to map.
+      \return  MapContext.  addr() gets the mapped address.  what() gets
+         any error message.  addr() returns nullptr on error.
+    */
+    PDAL_DLL MapContext mapFile(const std::string& filename, bool readOnly,
+        size_t pos, size_t size);
+
+    /**
+      Unmap a previously mapped file.
+      \param ctx  Previously returned MapContext
+      \return  MapContext indicating current state of the file mapping.
+    */
+    PDAL_DLL MapContext unmapFile(MapContext ctx);
+
+} // namespace FileUtils
 } // namespace pdal